What does it mean to be metabolically healthy obese?

     Over the past weekend, I read a summary statement for a research study by Camhi and Katzmarzyk, 2013.  I was intrigued because the exercise and health scientists explored the differences in body composition (e.g., % lean mass, fat mass, bone density, central fat tissue) between two groups of obese people. The people in the study were classified as metabolically healthy obese or abnormal obese. The summary statement did not indicate if obesity was determined by BMI, waist to hip ratio, waist circumference or some other measure.  It did say how the determination of healthy vs unhealthy (metabolically speaking) was made, and I thought this a teaching point.  (FYI: Simply put, metabolic refers to under the skin - cellular processes. So the researchers were not looking at whether or not there were mental health issues, or physical conditions like arthritis, in this group of obese persons.)  I also do not know why the researchers chose the criteria listed below to determine metabolic health, but each has been independently associated with poor health outcomes, like heart disease, in other studies.  Of the following measures, an obese person in the study who had 1 or less of them was considered metabolically healthy, and an obese person in the study who had 2 or more was considered metabolically abnormal.  

The measures were:

1. a blood pressure reading higher than 130/85 mm/Hg
2. a fasting glucose level greater than 100 mg/dl
3. a waist circumference greater than 102 cm men, 88 cm women (click here to convert to inches) 
4. triglyceride level (blood fats) higher than 150 mg/dl
5. hdl (good) cholesterol less than 40 mg/dl men, 50 mg/dl women

     I noticed that they did not use total cholesterol levels or LDL levels. 

     The aim of the study was to see if something about body composition was different between the two groups (could this difference explain the accumulating risk factors).  The researchers did find differences, which were specific to gender.  For most of the body composition measures they assessed(not described here), the metabolically healthy obese had lower values.  For example, both metabolically healthy men and women had lower fat mass and less stomach or trunk fat.  Most every measure was related to a type of adipose(fat) tissue, such that the more fat one had on their body, and in specific places, the more likely they were to have more than 2 of the risk factors and thus be metabolically unhealthy.
     Take home point.  Your absolute weight is not as important as your body composition and the 5 measures listed here are numbers you might want to pay attention to at your doctor's visits.